@2 - you mean that I can still use custom fields (i.e. drop down list) but it is not possible to edit the content of one list based on the selection in another list (i.e. the list of models based on the selected make) etc. Generally this will not be a problem ;)
On the other hand, if you remember I have asked a time ago if it will be possible to add a Service Log-Book integrated to a garage. I mean a database with information wneh you change engine and transmission oil, what oil do you use, when you change the coolant liquid, brakes liquid, brakes pads and rotors, hoses, belts, etc. Even a fuel log-book like spritmonitor.de which calculates the average fuel consumption of the vehicle compared to different conditions - season, tyre type, location, fuel type, fuel brand and even other vehicles of the same model etc.
I'm a webdeveloper also, so I can extend the source code myself to make it work as I need... I will think about the collection system some more time.